Abstract: To expand the resource utilization of fly ash, the desulfurization performance of fly ash as a desulfurization agent for wet flue gas desulfurization was studied using a flue gas desulfurization simulation device; And use the slurry of wet desulfurization with fly ash to prepare filling paste (desulfurization group), and compare the performance of ordinary fly ash filling paste (blank group); The pollution risks of Pb, Cr, Cd, Hg, Zn, As, Cu ions in two types of filling pastes were analyzed using the Nemero comprehensive pollution index method and the Hakanson potential ecological risk index method. The results show that under the conditions of wet desulfurization experiment, the desulfurization efficiency of coal ash slurry is high, and the duration above 95% increases with the increase of slurry concentration; The compressive strength of the desulfurization group at curing period of 3, 7, 14, and 28 days is 0.83, 1.59, 3.52, and 4.09 MPa, which is 1.5, 1.1, 1.26 and 1.3 times higher than that of the blank group with the same ratio. The slump, bleeding rate, initial setting time, and final setting time are reduced by 5.2%, 6.5%, 13.6%, and 11.1% compared to the blank group, respectively; The evaluation results using the Nemero index method indicate that the comprehensive pollution index of the desulfurization group is 0.5174, indicating a safe level of pollution. The comprehensive pollution index of the blank group is 0.9467, indicating a relatively safe level of pollution. The results of the Hakanson potential ecological risk index method indicate that the ecological hazard index of the desulfurization group is 8.848, while the ecological hazard index of the blank group is 31.509, and the risk level is mild. It can be seen that the risk of metal contamination in the filling paste prepared from desulfurized fly ash slurry has been reduced, making it suitable for use as a filling paste.